To date, brain-machine interfaces (BMIs) have sought to interface the brain with the external world using intrinsic neuronal signals as input commands for controlling external devices, or device-generated electrical signals to mimic sensory inputs to the nervous system. A new generation of neuroprostheses is now emerging that aims to combine neural recording, neural signal processing, and microstimulation functionalities in a single device, creating an artificial connection in the nervous system by converting neural activity recorded from one cortical area to electrical stimuli delivered to another cortical area, spinal cord, or muscles in real time.